A model system using rabbit intestinal mucosal explants has been developed to examine the characteristic ultrastructural damage to the brush border induced by enteropathogenic Escherichia coli 0111. In this model, as in others, bacterial adherence to the microvillous membranes occurred in two morphologically distinct stages. Initial attachment of enteropathogenic strains of E. coli to ileal mucosa appeared to be a goblet cells and the mucous layer covering the microvilli. The next stage involved binding of enteropathogenic strains of E. coli to the bases of the microvilli that became elongated and vesiculated. Eventually, large areas of brush border effacement occurred with close apposition between bacterial and enterocyte membranes, leading to cup and pedestal formation. With a relatively large inoculum of bacteria (10(8) cfu/ml) these changes occurred within 4 h, but even with much lower inocula (10(5) cfu/ml) localized areas of damage were seen within 8 h. Although the bacteriostatic antibiotic tetracycline (700 mg/L) inhibited bacterial replication, it did not prevent the characteristic damage produced by enteropathogenic strains of E. coli. Enteropathogenic strains of E. coli 0111 were able to produce attaching effacement to gastric, duodenal, jejunal, ileal, and colonic mucosa.